The present invention relates generally to automatic sliding doors. More particularly, the present invention relates to sensor and safety systems which control the operation of automatic sliding doors.
Sliding door systems of a type which are automatically operable for initiating an opening sequence upon sensing the motion or the presence of traffic at the doorway or receiving a command from a push plate, card reader, mat or other operation initiating device are now commonplace. A number of automatic door systems employ infra-red sensors to initiate the door opening sequence. The sensors sense traffic approaching the doorway by detecting changes in received active or passive infra-red radiation. Infra-red sensors also function as safety devices to ensure that the sliding doors do not inadvertently close.
Some conventional sliding door applications employ three separate sensor units--none of which are mounted to a sliding door. Two approach sensor units are positioned for coverage at each side of the sliding door. A threshold or safety sensor covers the threshold area in which the moving door panels travel. The approach sensors may conventionally be microwave field distortion devices or active infra-red motion sensing devices. The threshold sensors are conventionally presence sensing devices such as continuous infra-red beams.
Kornbrekke et al U.S. Pat. No. 4,823,010, assigned to the assignee of the present invention, discloses a novel threshold safety sensor for a sliding door system. The system employs infra-red transmitters and a photodiode for detecting traffic at or near the threshold of the sliding door system. The threshold sensor includes an elongated enclosure or rectangular housing which mounts at the underside of the door header or above the threshold. The threshold sensor is a safety sensor specifically adapted to detect the presence of an object at or near the threshold when the doors are opening or are in an opened position. A motion sensor mounted at the header or above the entranceway generates a signal to initiate the movement of the door to the opening position.
Boiucaner U.S. Pat. No. 5,142,152, assigned to the assignee of the present invention, discloses a sliding door sensor which mounts at the underside of the header above the threshold. Two arrays of infra-red transmitters are pulsed to provide an approach detection zone and a threshold detection zone. Both presence and motion detection are provided. The sensor also is capable of detecting dark objects.
Most sensor systems employed in conjunction with sliding doors are mounted to the headers or adjacent fixed frame supports for the sliding doors. Because of the sliding motion of the doors, providing electrical power to the sliding door panel itself, or a sensor signal communication from the sliding door panel has been problematical. Accordingly, the sliding doors for the vast majority of automatic sliding door systems do not have any electrical power, and few sliding door systems employ sensors mounted on the sliding doors. It should also be noted that because of the sliding movement of the doors, the sensor systems which are employed in controlling the operation of sliding door systems must take into account the movement of the sliding door itself. Accordingly, sophisticated signal processing may be required to properly account for the door movement.